This invention relates generally to systems for controlling the thermal and illumination environment within a structure, and more particularly, to an environmental control system of the type employing solar collectors for storing and retrieving solar energy.
Buildings that include a large area of glass have experienced the problem of excessive heat gain through the glass during exposure to direct sunlight. Also, these buildings often tend to cool off in the absence of sunlight. As a consequence, such buildings often require air conditioning during the day and large amounts of heat to maintain a comfortable temperature at night.
Various solutions to this problem have been attempted such as providing window shades or draperies over the windows to decrease the heat gain during exposure to sunlight and to offer additional insulation against the egress of heat at night. Also, tinted or reflecting glass has been provided to decrease the heat gain of a building during the day.
In the specific field of greenhouse operation, for example, the above-mentioned problems are particularly troublesome, and are compounded by the desire of greenhouse operators to provide optimum shading for a particular species of plant being grown. In order to provide this desired shading, operators have employed open mesh screens above the plants or under the roof of the greenhouse, and these screens had to be deployed or stored, in addition to coping with the cooling and heating problems discussed above.
Further regarding greenhouse operation, it has long been recognized that certain processes of a plant's physiology are triggered by specific conditions of the plant's environment, such as the duration and intensity of daylight and the ambient temperature. Consequently, it is highly desirable for a greenhouse operator to be able to accurately control these conditions in order to artificially induce a desired effect in the plants being grown, such as germination or budding. Unfortunately, the accurate control required to accomplish these ends is difficult to achieve and very costly when undertaken in large scale by methods known heretofore.
Accordingly, there has existed a need for a convenient and effective method and apparatus for controlling the temperature and amount of sunlight within any structure having a large transparent wall area. As will become apparent from the following, the present invention satisfies that need.